Stainless steel foil and method of production of same
The present invention has as its object to provide thickness 60 μm or less ultra-thin stainless steel foil which secures high thickness precision and simultaneously secures plastic deformability and good elongation at break, that is, secures good press-formability (deep drawability). The present invention solves this problem by ultra-thin stainless steel foil which has three or more crystal grains in a thickness direction, has a recrystallization rate of 90% to 100%, and has a nitrogen concentration of a surface layer of 1.0 mass % or less. For this reason, there is provided a method of production of stainless steel foil comprising rolling stainless steel sheet, then performing final annealing and making a thickness 5 μm to 60 μm, wherein a rolling reduction ratio at rolling right before final annealing is 30% or more, a temperature of final annealing after rolling is 950° C. to 1050° C. in the case of austenitic stainless steel and 850° C. to 950° C. in the case of ferritic stainless steel, and a nitrogen content in atmospheric gas in final annealing is 0.1 vol % or less, whereby ultra-thin stainless steel foil can be produced.
1. Stainless steel foil with a thickness of 5 μm to 40 μm, which has a number of crystal grains of three or more in a thickness direction, has a recrystallization rate of 90% to 100%, and has a nitrogen concentration of a surface layer of 1.0 mass % or less, and
wherein a surface roughness Rz is 100 nm or more and 1/10 or less of the thickness, and
wherein the number of crystal grains in the thickness direction is obtained by measuring the crystal grain size at any cross-section in the thickness direction based on JIS G0551 to calculate the average crystal grain size, dividing the thickness by the average crystal grain size.
2. The stainless steel foil according to claim 1 , wherein an elongation at break is 10% or more.
3. The stainless steel foil according to claim 1 , wherein said stainless steel foil is ferritic stainless steel.
4. The stainless steel foil according to claim 1 , wherein said stainless steel foil is austenitic stainless steel.
5. The stainless steel foil according to claim 1 , wherein at least one surface of said stainless steel foil has a resin film laminated on it.
6. A method of production of stainless steel foil according to claim 1 comprising rolling stainless steel sheet, then performing final annealing and making a thickness 5 μm to 40 μm and a surface roughness Rz of 100 nm or more and 1/10 or less of the thickness, the method of production of stainless steel foil comprises two or more times of rolling, wherein a rolling reduction ratio at rolling right before final annealing is 30% or more in the case of austenitic stainless steel and 50% or more in the case of ferritic stainless steel, a nitrogen content in atmospheric gas in final annealing is 0.1 vol % or less, and a temperature of said final annealing is 950° C. to 1050° C. in the case of austenitic stainless steel and 850° C. to 950° C. in the case of ferritic stainless steel.
7. The stainless steel foil according to claim 2 , wherein said stainless steel foil is ferritic stainless steel.
8. The stainless steel foil according to claim 2 , wherein said stainless steel foil is austenitic stainless steel.
9. The stainless steel foil according to claim 2 , wherein at least one surface of said stainless steel foil has a resin film laminated on it.